Battery separator and nonaqueous electrolyte battery
View Patent ↗A nonaqueous electrolyte battery of the present invention includes a positive electrode having a positive active material capable of intercalating and deintercalating a lithium ion, a negative electrode having a negative active material capable of intercalating and deintercalating a lithium ion, a separator interposed between the positive electrode and the negative electrode, and a nonaqueous electrolyte. The heat generation starting temperature of the positive electrode is 180° C. or higher. The separator includes heat-resistant fine particles and a thermoplastic resin. The proportion of particles with a particle size of 0.2 μm or less in the heat-resistant fine particles is 10 vol % or less and the proportion of particles with a particle size of 2 μm or more in the heat-resistant fine particles is 10 vol % or less. The separator effects a shutdown in the range of 100° C. to 150° C.
1. A battery separator comprising:
heat-resistant fine particles; and
a thermoplastic resin,
wherein the heat-resistant fine particles along with a binder constitute a heat-resistant layer,
the thermoplastic resin constitutes a shutdown layer formed of a heat-shrinkable microporous film,
the heat-resistant layer and the shutdown layer are integrated into a multilayer structure,
the shutdown layer has a thickness A (μm) of 5 to 30, the heat-resistant layer has a thickness B (μm) of 1 to 10, a sum of A and B is 6 to 23, and a ratio A/B is 1/2 to 4,
a content of the heat-resistant fine particles in the heat-resistant layer is 50 vol % or more of a total volume of components in the heat-resistant layer,
a proportion of particles with a particle size of 0.2 μm or less in the heat-resistant fine particles is 10 vol % or less and a proportion of particles with a particle size of 2 μm or more in the heat-resistant fine particles is 10 vol % or less, and
a shutdown is effected in a range of 135° C. to 150° C.
2. The battery separator according to claim 1 , wherein a thermal shrinkage ratio in a width direction is 10% or less at 200° C.
3. The battery separator according to claim 1 , wherein the content of the heat-resistant fine particles in the heat-resistant layer is 80 vol % or more of the total volume of components in the heat-resistant layer.
4. The battery separator according to claim 1 , wherein the heat-resistant fine particles are inorganic fine particles.
5. The battery separator according to claim 4 , wherein the inorganic fine particles include fine particles of at least one selected from the group consisting of alumina, silica, BaTiO 3 , boehmite, zeolite, and kaoline.
6. The battery separator according to claim 1 , wherein the heat-resistant fine particles include plate-like particles.
7. The battery separator according to claim 1 , wherein the heat-resistant layer has a thickness of 2 μm to 6 μm.
8. The battery separator according to claim 1 , wherein the thermoplastic resin includes polyolefin.
9. The battery separator according to claim 1 , wherein the heat-resistant fine particles have an average particle size of 1.5 μm or less.
10. A nonaqueous electrolyte batter comprising:
a positive electrode having a positive active material capable of intercalating and deintercalating a lithium ion;
a negative electrode having a negative active material capable of intercalating and deintercalating a lithium ion;
a separator interposed between the positive electrode and the negative electrode; and
a nonaqueous electrolyte,
wherein a heat generation starting temperature of the positive electrode is 180° C. or higher, and
wherein the separator is the battery separator according to claim 1 .
11. The nonaqueous electrolyte battery according to claim 10 , wherein a thermal shrinkage ratio of the separator is 10% or less at a temperature T (° C.) that is 10° C. lower than the heat generation starting temperature of the positive electrode (where an upper limit of T is 200° C.).
12. The nonaqueous electrolyte battery according to claim 10 , wherein a width of the separator is larger than that of the negative electrode at a temperature T (° C.) that is 10° C. lower than the heat generation starting temperature of the positive electrode (where an upper limit of T is 200° C.).
13. The nonaqueous electrolyte battery according to claim 10 , wherein the positive active material is at least one selected from the group consisting of the following: a spinel-type lithium-containing complex oxide expressed as a general formula Li 1+t Mn (2−x) M 1 x O 4 (where M 1 is at least one element selected from the group consisting of Fe, Ni, Mg, Zn, Co, Cr, Al, B, V, Si, Sn, Nb, Ta, Cu, Mo, Ti, and W, −0.1≦t≦0.1, and 0≦x≦0.6); an olivine-type lithium-containing complex oxide expressed as a general formula LiM 2 PO 4 (where M 2 is Co, Ni, Mn, or Fe); a lithium-containing complex oxide having a layered crystal structure expressed as a general formula Li (1+a) M 3 2b Mn (0.5−b) Ni (0.5−b) O 2 (where M 3 is at least one element selected from the group consisting of Fe, Mg, Zn, Co, Cr, Al, B, V, Si, Sn, Nb, Ta, Cu, Mo, Ti, and W, −0.1<<0.1, and 0≦b≦0.05); and a lithium-containing complex oxide expressed as a general formula Li (1+y+α) Ni (1−y−z−δ)/2 Mn (1−y−z−δ)/2 M 4 z O 2 (where M 4 is at least one element selected from the group consisting of Ti, Cr, Fe, Co, Cu, Zn, Al, Ge, Sn, Mg, and Zr, −0.1≦y≦0.1, −0.05≦α≦0.05, 0≦z<0.45, and −0.24≦δ≦0.6).
14. The nonaqueous electrolyte battery according to claim 10 , wherein a content of the heat-resistant fine particles in the heat-resistant layer of the separator is 80 vol % or more of a total volume of components in the heat-resistant layer.
15. The nonaqueous electrolyte battery according to claim 10 , wherein the heat-resistant fine particles of the separator are inorganic fine particles.
16. The nonaqueous electrolyte battery according to claim 15 , wherein the inorganic fine particles include line particles of at least one selected from the group consisting of alumina, silica, BaTiO 3 , boehmite, zeolite, and kaoline.
17. The nonaqueous electrolyte battery according to claim 10 , wherein the heat-resistant fine particles of the separator include plate-like particles.
18. The nonaqueous electrolyte battery according to claim 10 , wherein the heat-resistant layer of the separator has a thickness of 2 μm to 6 μm.
19. The nonaqueous electrolyte battery according to claim 10 , wherein the thermoplastic resin of the separator includes polyolefin.
20. The nonaqueous electrolyte battery according to claim 10 , wherein the shutdown layer of the separator is located on a negative electrode side.
21. The nonaqueous electrolyte battery according to claim 10 , wherein the shutdown layer of the separator is not in contact with the positive active material.
22. The nonaqueous electrolyte battery according to claim 10 , wherein the heat-resistant fine particles of the separator have an average particle size of 1.5 μm or less.
23. The battery separator according to claim 1 , wherein the shutdown layer has a thickness of 16 μm or less.
24. The battery separator according to claim 1 , wherein a content of the binder in the heat-resistant layer is 1 to 20 vol % of a total volume of components in the heat-resistant layer.
25. The battery separator according to claim 1 , wherein the binder includes at least one selected from the group consisting of an ethylene-vinyl acetate copolymer (having 20 to 35 mol % of a structural unit derived from vinyl acetate); an ethylene-acrylic acid copolymer; fluoro-rubber; styrene-butadiene rubber; carboxymethyl cellulose; hydroxyethyl cellulose; polyvinyl alcohol; polyvinyl butyral; polyvinyl pyrrolidone; poly-N-vinylacetamide; a cross-linked acrylic resin; polyurethane; and an epoxy resin.
26. The battery separator according to claim 1 , wherein the heat-resistant line particles have an average particle size of 0.3 μm or more.
27. The nonaqueous electrolyte battery according to claim 10 , wherein the shutdown layer of the separator has a thickness of 16 μm or less.
28. The nonaqueous electrolyte battery according to claim 10 , wherein a content of the binder in the heat-resistant layer of the separator is 1 to 20 vol % of a total volume of components in the heat-resistant layer.
29. The nonaqueous electrolyte battery according to claim 10 , wherein the binder of the separator includes at least one selected from the group consisting of an ethylene-vinyl acetate copolymer (having 20 to 35 mol % of a structural unit derived from vinyl acetate); an ethylene-acrylic acid copolymer; fluoro-rubber; styrene-butadiene rubber; carboxymethyl cellulose; hydroxyethyl cellulose; polyvinyl alcohol; polyvinyl butyral; polyvinyl pyrrolidone; poly-N-vinylacetamide; a cross-linked acrylic resin; polyurethane; and an epoxy resin.
30. The nonaqueous electrolyte battery according to claim 10 , wherein the heat-resistant fine particles of the separator have an average particle size of 0.3 μm or more.
31. The nonaqueous electrolyte battery according to claim 10 , wherein the shutdown layer of the separator is not in contact with the positive active material, and a charging potential of the positive electrode is 4.3 V or more.
32. The battery separator according to claim 1 , wherein the heat-resistant layer has a porosity of 20% to 60%.
33. The battery separator according to claim 1 , wherein the whole separator has a porosity of 30% to 70%.
34. The nonaqueous electrolyte battery according to claim 10 , wherein the heat-resistant layer has a porosity of 20% to 60%.
35. The nonaqueous electrolyte battery according to claim 10 , wherein the whole separator has a porosity of 30% to 70%.
36. The battery separator according to claim 1 , wherein the microporous film is formed by a solvent extraction method, a dry drawing method, or a wet drawing method.
37. The nonaqueous electrolyte battery according to claim 10 , wherein the microporous film is formed by a solvent extraction method, a dry drawing method, or a wet drawing method.